counting function on data frame in R

Question

I have the following data frame:

> Mice
        Blood  States  Minute
1       0.875     X0 0.8352569
2       0.875     A2 0.7551901
3       0.625     X0 1.4508139
4       0.625     A1 0.7876343
5       0.375     X0 1.1345252
6       0.125     X0 0.8699363
7       0.375     X0 0.9378742
8       1.125     H1 0.9769522
9       0.625     X0 0.4716321
10      0.875     H1 0.9935999
11      0.625     X0 1.0025917
12      0.375     A1 1.0703999
13      0.375     X0 1.3044854
14      0.875     H1 0.6720436
15      0.875     A1 1.0431863

So every mouse has some value of drugs in their "Blood", and their "State" is checked. This is just a piece of my data frame, but the mice can be in 4 different states. "Minute" is whenever something occurs to the mice, does not matter what.

For every value of "Blood", the mice can be in either of the 4 different states, and I want to count how many observations I have in each category.

The count() function with both columns Blood and States did not work because "States" is a factor column

Answer 1

To operate on factor levels, you can use tapply or by . If you have discrete scale for Mice$Blood , convert it to a factor as well:

> by(mice$States, as.factor(mice$Blood), function(x) summary(factor(x)))

as.factor(mice$Blood): 0.125
X0 
 1 
------------------------------------------------------------------------------------------------ 
as.factor(mice$Blood): 0.375
A1 X0 
 1  3 
------------------------------------------------------------------------------------------------ 
as.factor(mice$Blood): 0.625
A1 X0 
 1  3 
------------------------------------------------------------------------------------------------ 
as.factor(mice$Blood): 0.875
A1 A2 H1 X0 
 1  1  2  1 
------------------------------------------------------------------------------------------------ 
as.factor(mice$Blood): 1.125
H1 
 1 

The returned object is a list, so you may capture it and use for your purposes.